$$rAF callback not fired in iOS9, WKWebView

[sapieneptus]

Specifically, the requestAnimationFrame(cb) doesn't seem to be firing it's callback. Works on other browsers, but iOS9 WKWebView seems not to work.

I've read some hack solutions but curious if there isn't an Angular solution.

[sapieneptus]

To provide a bit more context, where the issue is manifesting is in this code:

$animate.on('enter', myElement, function(el, phase) {
        console.log("something was added");
      });

The log is never called in the WKWebView. I've tracked it down to angular:notifyProgress():

function notifyProgress(runner, event, phase, data) {
        runInNextPostDigestOrNow(function() {
          var callbacks = findCallbacks(element, event);
          console.log({callbacks:callbacks});
          if (callbacks.length) {
            // do not optimize this call here to RAF because
            // we don't know how heavy the callback code here will
            // be and if this code is buffered then this can
            // lead to a performance regression.
            $$rAF(function() {
              console.log("Callback");  //Never called
              forEach(callbacks, function(callback) {
                callback(element, phase, data);
              });
            });
          }
        });
        runner.progress(event, phase, data);
      }

Let me know if I can provide any more info!

[Narretz]

I have looked through the page, but I can't find the "hack solution", not one specific to webkit that is. Can you point me to it?

[sapieneptus]

Hi @Narretz ,

After much exploration, I think the problem may have been related to the webview not being visible at the time of testing. Apparently, if webview.hidden=YES, iOS imposes some fairly restrictive limitations on what the webview can do, including refresh rates (to conserve energy, I suppose).

Interestingly, if webview.hidden=NO but webview.alpha=0, the webview behaves as expected. Go figure.

[Narretz]

@sapieneptus Thanks for the update! Do you consider this issue to be solved, then?

[Narretz]

I think we can close this. Afaik, some browsers disable / slow down animation frames when the tab / window is not visible. It's possible that this was the issue - a similar issue is being tracked here: #12842